1. Field of the Invention
The present invention relates to an illuminant material and an illuminant device, especially as it relates to organic electroluminescent material and an organic electroluminescent material to be used for electroluminescent devices.
2. Description of the Prior Art
LCD displays are becoming more and more popular, but they still have the disadvantages of narrow angle view, slow response time for high-speed animation, high power consumption for a back light panel and are not suitable for producing a large LCD screen. In such circumstances, research on a next generation flat panel display apparatus and a planar light source illumination for an organic light-emitting diode (OLED) of a self-luminescence, wide angle view, low power consummation, simple process for manufacturing, low cost, fast response time and entire color scheme are actively conducted.
FIG. 1 shows a macromolecular light-emitting diode with single layer structure. The organic light-emitting diode 10 comprises a transparent substrate 12, a transparent anode 14, an organic electroluminescent layer 16 and a cathode 18. When DC voltage is applied to an organic light-emitting diode 10, holes are injected in the other from an anode 14. Meanwhile, electrons are injected in the other from a cathode 18. Now, owing to an external electrical field it creates a potential difference that causes carriers to drift, contact and bind from one end of an organic electroluminescent layer 16 to the other. After electronics and holes bind together, then excitons are created for exciting a luminescent molecule which emits from an organic electroluminescent layer 16. The electroluminescent molecule releases their energy as light. This luminescent molecule typically comprises an organic electroluminescent material of small molecule and macromolecular.
Many organic materials for an electroluminescent layer have already developed for a long time. In 1987, C. W. Tang and S. A. Vanslyke aime at the organic electroluminescent layer to release an organic thin film layer and the double layer structure for a hole/electron transmissive thin film layer. Lett's luminous chrominance can be dependent upon the variance of the difference in band gap between the ground-state and the excited-state of material. This is so-called the fluorescence structure. Besides the 1998, Baldo with a few people doping red phosphorescence dyes into Alq3, and they discover the efficiency of energy transmission between Alq3 and PtOEP almost reaches 90%. This result causes the triple-state energy transmission between Alq3 and PtOEP that can be passed by an implementation of Dexter energy transmission process. It is therefore quite as important discovery for producing the high efficiency of the EL device. In 1999, Forrest, Burrow, Thompson and Baldo publish the organic electroluminescent material that is designed by metallic chelation with Ir(ppy)3 fac-tris(2-phenylpyridine)iridium structure. It provides for making a green light-emitting device (Appl. Phys. Lett 74:4, 1999). Furthermore, owing to this luminous structure it emits phosphorescence, phosphorescent efficiency improvement is obtained. Over the past years, Forrest with a few people have proposed many related derivatives such as Ir(ppy)3 and PtOEP, and have obtained patent applications such as U.S. Pat. Nos. 6,573,651, 6,303,238, 6,579,632 etc. Due to Ir(ppy)3 it will be far more stable than Alq3, and an organic light-emitting diode material is suitable for use in phosphorescent family. The mechanism of phosphorescent belongs to the class of the triplet state of the luminance, no matter what the probability of occurrence and the luminous efficiency are, they are all better than phosphorescent light emitting structure.
Therefore, the Ir(ppy)3 derivatives devote more and more attention, and it widely uses the organic electroluminescent material and light-emitting device. On the other hand, there are also some disadvantages, such as it spends too much time for light attenuation, the severe quenching of triplet state causes components that are life limited and low color purity etc.
In order to solve the above-mentioned disadvantages of Ir(Ppy)3, the present invention provides an organic electroluminescent material and an electroluminescent device to solve the above-mentioned problem.